THE CUM ACE A 



185 



When the lateral plates are removed, the conformation of the head 

 and the position of the eye show some similarity to the arrange- 



"%..-; 



ment met with in the Oedicerotidae 

 among the Amphipoda. The two eyes 

 are distinct in the embryo, and in one 

 genus (Nannastacus) also in the adult. 



Appendages. — The antenmdes rarely 

 have both flagella well developed, the 

 inner being usually reduced or absent. 

 The antennae differ remarkably in the 

 two sexes. In the female (Fig. 112, a") 

 they are vestigial, while in the male they 

 consist of a stout peduncle of five seg- 

 ments, of which the last two are enlarged 

 and clothed with a brush of long setae, 

 Avhile the flagellum is filiform and may 

 exceed the length of the body (Fig. 1 1 3). 

 In life this long flagellum is usually 

 carried folded close to the side of the 

 body, protected by the lower edge of the 

 carapace and by the pleural plates of the 

 abdomen, or in a special groove which 

 runs along the sides of the abdominal 

 somites. In the genus LamjyrojJS the 

 antennal flagella of the male are short 

 and stout, and are used as clasping-organs 

 to hold the female. 



The mandibles never carry a palp, but 

 in other respects conform to the type 



characteristic of the Peracarida. In the ;,„^^ ^^^^^,^ ^^^^^. ,,^ „^,, ^^,^. 

 Leuconidae and in the genus Diastijloides °U^'f^ '' o'-a .ovary ; ps, vseudo- 

 the body of the mandible is short and 

 triangular and the row of 

 molar process is styliform. 



Fi(i. 112. 



Diagram of anterior part of 

 body of DiastfiUs, 9, from above, 

 showing the internal organs, a', 

 antennule ; o", antenna ; hr, 

 branchial epipodite of first maxil- 

 liped enclosed in branchial cavity 

 at side of carapace ; e, eyes, coal- 

 esced into one ; ex, exopodite oi 

 first maxilliped, forming the re- 

 spiratory siphon ; fr, lateral 

 branch of "frontal fissure" be- 

 tween the head and the lateral 

 plate of pseudorostrum ; h, heart ; 



rostrum. (After Sars.) 



spines is reduced. In Cam]}ylaspis the 



Fig. 113. 

 Pterocuma pediiMtum, (J, from the Caspian Sea. (After Sars, from Ency. Brit.) 



The maxillulae (Fig. 114, A), except in Flatyaspis and Para- 

 lamprops, carry a retro verted palp as in Tanaidacea and Lopho- 

 gastridae. The maxillae (Fig. 114, B) with their two terminal 



